Large-scale reorganization of corticofugal fibers after neonatal hemidecortication for functional restoration of forelimb movements

Authors

  • Masahito Takahashi,

    1. Department of Developmental Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan
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    • *

      Present address: Department of Orthopaedic Surgery, Kyorin University, Mitaka, Japan

    • M.T., A.V. and T.U. contributed equally to this work.

  • Anusara Vattanajun,

    1. Department of Physiology, Phramongkutklao College of Medicine, Bangkok, Thailand
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    • M.T., A.V. and T.U. contributed equally to this work.

  • Tatsuya Umeda,

    1. Department of Developmental Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan
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    • *

      Present address: Department of Orthopaedic Surgery, Kyorin University, Mitaka, Japan

  • Kaoru Isa,

    1. Department of Developmental Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan
    2. Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, Kawaguchi, Japan
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  • Tadashi Isa

    1. Department of Developmental Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan
    2. Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, Kawaguchi, Japan
    3. School of Life Science, the Graduated University for Advanced Sciences, Hayama, Japan
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Dr Tadashi Isa, 1Department of Developmental Physiology, as above.
E-mail: tisa@nips.ac.jp

Abstract

As an experimental model to study the mechanism of large-scale network plasticity of the juvenile brain, functional compensation after neonatal brain damage was studied in rats that received unilateral decortication at postnatal day 5. These animals exhibited a marked ability in reaching and grasping movements in the contralesional side of the forelimb when tested at 10–14 weeks of age. Additional lesion of the sensorimotor cortex in the remaining contralesional hemisphere at this stage resulted in severe impairment of both forelimbs. It was suggested that the sensorimotor cortex on the contralesional side was controlling the movements of both forelimbs. Following the injection of an anterograde tracer into the remaining sensorimotor cortex, the corticofugal axons from the remaining sensorimotor cortex were found to issue aberrant projections to the contralateral red nucleus, contralateral superior colliculus, contralateral pontine nuclei, ipsilateral dorsal column nucleus and ipsilateral gray matter of the cervical spinal cord, all of which appeared to be necessary for the control of contralesional forelimb movements. These results suggest that the forelimb movements on the contralesional side were compensated by large-scale reorganization of the corticofugal axons from the remaining sensorimotor cortex.

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